'\" te
.\" Copyright (c) 2006, Sun Microsystems, Inc.
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.TH DDI_BTOP 9F "Jan 16, 2006"
.SH NAME
ddi_btop, ddi_btopr, ddi_ptob \- page size conversions
.SH SYNOPSIS
.nf
#include <sys/ddi.h>
#include <sys/sunddi.h>



\fBunsigned long\fR \fBddi_btop\fR(\fBdev_info_t\fR \fI*dip\fR, \fBunsigned long\fR \fIbytes\fR);
.fi

.LP
.nf
\fBunsigned long\fR \fBddi_btopr\fR(\fBdev_info_t\fR \fI*dip\fR, \fBunsigned long\fR \fIbytes\fR);
.fi

.LP
.nf
\fBunsigned long\fR \fBddi_ptob\fR(\fBdev_info_t\fR \fI*dip\fR, \fBunsigned long\fR \fIpages\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH DESCRIPTION
This set of routines use the parent nexus driver to perform conversions in page
size units.
.sp
.LP
The \fBddi_btop()\fR function converts the given number of bytes to the number
of memory pages that it corresponds to, rounding down in the case that the byte
count is not a page multiple.
.sp
.LP
The \fBddi_btopr()\fR function converts the given number of bytes to the number
of memory pages that it corresponds to, rounding up in the case that the byte
count is not a page multiple.
.sp
.LP
The \fBddi_ptob()\fR function converts the given number of pages to the number
of bytes that it corresponds to.
.sp
.LP
Because bus nexus may possess their own hardware address translation
facilities, these routines should be used in preference to the corresponding
DDI/DKI routines \fBbtop\fR(9F), \fBbtopr\fR(9F), and \fBptob\fR(9F), which
only deal in terms of the pagesize of the main system MMU.
.SH RETURN VALUES
The \fBddi_btop()\fR and \fBddi_btopr()\fR functions return the number of
corresponding pages. \fBddi_ptob()\fR returns the corresponding number of
bytes. There are no error return values.
.SH CONTEXT
This function can be called from user, interrupt, or kernel context.
.SH EXAMPLES
\fBExample 1 \fRFind the size (in bytes) of one page
.sp
.in +2
.nf
pagesize = ddi_ptob(dip, 1L);
.fi
.in -2

.SH SEE ALSO
.BR btop (9F),
.BR btopr (9F),
.BR ptob (9F)
.sp
.LP
\fIWriting Device Drivers\fR
